The present invention relates to a method of fabricating an inductor, and particularly to a method of fabricating a coil-embedded inductor.
Generally, an inductor comprises an iron core wound by a coil. Coil-embedded inductors are utilized to provide an inductor with reduced volume.
Refer to FIGS. 1A to 1D and 2A to 2D together. FIGS. 1A, 1B, 1C, and 1D show a coil of a conventional coil-embedded inductor. FIGS. 2A, 2B, 2C, and 2D show a conventional coil-embedded inductor. In fabrication of the coil-embedded inductor, a wrapped coil 1 with two terminals 10 is enclosed by a core housing 20, exposing the terminals 10, as shown in FIG. 2A and FIG. 2B.
Ferrite powder and ferromagnetic metal powder are widely used to form the iron core by powder die-casting. With ferrite powder, powder sintering is further required to increase inductance and strength of the iron core. As a result, ferromagnetic metal powder is utilized more frequently due to enhanced magnetic flux density and DC-bias characteristics.
U.S. Publication No. 2001/0016977 discloses a method of fabricating a coil-embedded inductor, in which an iron core base 2 illustrated in FIG. 2 of this art thereof is formed previously, and a coil is inserted therein later. Press forming completes fabrication of the coil-embedded inductor. Detailed process of the method is illustrated in FIG. 5A to FIG. 5I of the related art thereof. This method, however, requires iron core base 2 to be fabricated prior to press forming, such that a gap may occur between the iron core base 2 and the coil due to non-uniform density distribution. The area near the gap shows increased magnetic flux density, achieving magnetic saturation easily, affecting the electrical characteristics of the coil-embedded inductor.
U.S. Publication No. 2003/0141952 discloses another method of fabricating a coil-embedded inductor, described with reference to FIG. 3 and FIG. 11A to FIG. 11D of this art thereof. The terminals of the coil are bent to a single plane. The coil is then placed in a die for formation of the coil-embedded inductor. Due to this reason, resistance of the coil-embedded inductor will increase from the bent terminals of the coil results in heat production at high electric current levels, affecting the electrical characteristics of the coil-embedded inductor.
As a result, there is a need for a coil-embedded inductor with a core housing having uniform density distribution.